Conventionally, in a vertical pump, a rotor having a plurality of blades extending radially in a plane perpendicular to a main spindle of the pump is arranged at a lower position within a easing of the pump and is rotated to execute drawing or suction of water from a lower end of the casing.
However, this vertical pump has the following disadvantages. That is, since the pump comprises the plurality of blades which are so spread as to extend radially in the plane perpendicular to the main spindle of the pump, toward the casing, a passing area of water stream or flow is limited or narrowed. Particularly, in a case where sewage is sucked or drawn, cloths and solid matters which may be contained in the sewage lodge within the pump.
Further, a centrifugal pump is known which is disclosed in Japanese Patent Laid-Open No. SHO 57-181997, as a pump having a single helical blade.
However, such a centrifugal pump has the following disadvantage. That is, since water drawn in a direction of the main spindle of the pump flows in a direction perpendicular to the main spindle, solid matters and the like lodge within the pump.
Furthermore, depending upon water pumping environment, there may be a case where a vertical type non-blocked pump is required.
It is an object of the invention to provide a vertical pump which is non-blocked and which is large in lift and in discharge quantity or delivery.